It is necessary to use antibiotics to treat patients, and this method has been commonly used in every big hospital. However, under the excessive use of antibiotics, drug resistance of bacteria has gradually increased. Therefore, when patients are infected or being ill, it is important to distinguish whether this microorganism is susceptible or resistant to antibiotics that are used to treat patients. Besides, the application for detection of drug resistance in human infection diseases, fast detection of drug resistance of microorganisms is also very important in the field of agriculture.
Cells can be separated into two fundamentally different types: eukaryotic and prokaryotic cells. Bacteria belong to prokaryote. The essential components of bacteria include cell wall composed of peptidoglycan that gives rigid support and protects cell against osmotic pressure, cytoplasm that is the site of transport and oxidative, ribosome that serves as the site of mRNA translation, and chromosome that is the genetic material passed generation to generation. There are also some nonessential components like capsule which protects cells from phagocytosis, flagellum that increases the motility of cells, pilus or fimbria that provides the adherence to cell surface and the attachment to bacteria during conjugation, and plasmid that contains a variety of genes for antibiotic resistance and enzymes.
Escherichia coli is a gram-negative rod, about 3-5 μm*0.5 μm. Escherichia coli lives in gut where it helps to digest food and produces Vitamin K. E. coli causes a variety of diseases both within and outside the intestinal tract by pili, capsule, endotoxin and exotoxins. The most common diseases caused by E. coli is urinary tract infection, gram-negative rod sepsis, neonatal meningitis and the agent most frequently associated with traveler's diarrhea.
Penicillin acts by inhibiting transpeptidase, the enzymes that catalyze the final cross-linking step in the synthesis of peptidoglycan. Penicillin-treated cells die by rupture as a result of the influx of water causing the high-osmotic-pressure interior of the bacterial cell, and ampicillin has activity against several gram-negative rods that the earlier penicillin did not have. The damage of bacteria cell wall caused by antibiotics changes the compartment and shape of bacteria thus alternates the refractive index of bacteria.
There are three mechanisms that mediate bacterial resistance to drugs. (i) Bacteria produce enzymes that inactivate the drug, for example, β-lactamase, which can inactivate penicillin by cleaving the β-lactam ring of drugs. (ii) Bacteria with mutant protein on the ribosomal can result in resistance to streptomycin. (iii) Bacteria can change their permeability so that the drug effect on intracellular concentration can not work. Drug resistance of most bacteria is due to genetic change, chromosomal mutation, or transformation of plasmid. The frequency of spontaneous mutation, usually ranging from 10−7 to 10−9, is much lower than that of acquisition of resistance plasmid. In this case, when it comes to clinical problem, chromosomal resistance occurs less than plasmid-mediated resistance.
Surface plasmon was first predicted by Ritchie in 1957 and verified by Powell and Swan in 1960. Optical surface plasmon resonance (SPR) was not demonstrated until 1968 by Otto. Ever since, SPR is widely applied to the study of biomaterial process including immunodiagnostics and kinetic analysis of antibody-antigen interactions, and also provides valuable dynamic information which includes gas adsorption, binding kinetics, epitope mapping, and film thickness measurements.
Although some prior art (1) Backman, V., L. T. Perelman, et al. (2000). “Detection of preinvasive cancer cells.” Nature 406(6791):35; (2) Arimoto, H., T. Oishi, et al. (2001). “Affinity of a vancomycin polymer with bacterial surface models.” Tetrahedron Letters 42(19): 3347-3350; (3) Chen, K. H., C. C. Hsu, et al. (2002). “Measurement of wavelength shift by using surface plasmon resonance heterodyne interferometry.” Optics Communications 209(1-3): 167; (4) Chien, F. C., K. T. Huang, et al. (2005). Direct detection of the interaction of tiny analytes with receptors using an advanced plasmonic biosensor. Progress in Biomedical Optics and Imaging—Proceedings of SPIE; and (5) Choi, J. W., K. W. Park, et al. (2005). “Cell immobilization using self-assembled synthetic oligopeptide and its application to biological toxicity detection using surface plasmon resonance.” Biosensors and Bioelectronics 20(11): 2300-2305, have provided some progress, some defects of the prior art need to be modified.